AGL's Liddell power station is a "grandmother" plant that shouldn't receive funds more usefully invested elsewhere to improve Australia's energy prospects, Christiana Figueres, the former United Nations climate chief, said.

Ms Figueres, who as executive secretary of the UN Framework Convention on Climate Change oversaw the Paris climate agreement, said time is running out for Australia to get its energy and carbon policies in order.

"The time is short," Ms Figueres told Fairfax Media during a visit to Australia. "I think 10 years of dithering is enough."

Her comments come as Prime Minister Malcolm Turnbull met AGL executives on Monday to discuss the future of Liddell. AGL has said it was committed to shutting the 46-year-old Hunter Valley power plant by 2022, while the government is pressing to extend its life by five years to head off possible electricity shortages.

The Greens, meanwhile, are planning to seek support from Labor and other parties for a bill that would prohibit Commonwealth government aid for coal-fired power stations whether existing or new ones.

Liddell was "a grandmother plant that would need quite a bit of refurbishing for a very short term operation," Ms Figueres. "If [AGL] are going to invest that money they may as well invest it into something they are going to operate for a long time."

The former Costa Rican diplomat, who will address a CityTalks event at the Sydney Town Hall on Tuesday on how cities can lead climate action, said governments should focus on what was to be gained from exiting fossil fuel industries.

"Australia is actually facing a very bright future with limitless renewable energy resources to begin with," Ms Figueres said. It also has many of the minerals such as lithium used in batteries that "can be the new exporting engines in the economy".

Australia's current level of renewable energy could also triple its share of the electricity market to 50 per cent provided integration issues were resolved, she said.

Beyond Trump

Global efforts to tackle climate change would continue despite the decision by the Trump administration to withdraw the US from the Paris accord. Ms Figueres said the agreement conditions the US signed up for meant a formal exit by America won't happen until 2020.

Even so, since President Trump's decision, nine US states, more than 300 cities and 1000 corporations had agreed to meet America's Paris target of cutting 2005-level greenhouse gas emissions 26-28 per cent by 2025.

"It's not entirely unreasonable that the US might actually reach the Paris goals ... even without the help of the White House," Ms Figueres said, noting those who plan to stay the course alone account for half the US population.

While the massive destruction wrought by powerful hurricanes Harvey and Irma in the past fortnight was unlikely to alter the stance of President Donald Trump, many people would be prompted to reflect on the risks of a warming planet.

"Those events are typical of the kind of acceleration and intensification of natural disasters that we are already seeing and will continue to see with climate change," she said.

"They are a reminder of the fact we are not doing as much as we need to do on global emissions reduction, in particular for low-lying islands and vulnerable populations."

Coal bar

The Greens bill, expected to go before the Senate next month, would aim to block Turnbull government moves to extend the life of coal-fired power stations "that make global warming worse and threaten our way of life", Adam Bandt, the Greens climate change and energy spokesman, said.

"We wouldn't let the government subsidise asbestos and we shouldn't let them subsidise coal," Mr Bandt said, adding that "Labor needs to choose which side they are on."